Millions of customers can now login and pay with the payment and shipping information stored in their Amazon account. Join thousands of merchants and start building a strong, loyal customer base. Amazon Login and Pay with Amazon makes it easy for customers to buy what they want, and get on with their lives. Forget countless usernames and passwords — your Amazon account details are all you need.
Amazon Payments is available as a Magento extension/module, reducing time-to-market & development costs.
Here's a video which positions the offering.
Here are some example Magento sites that have implemented Amazon Payments:
Finally, here's an informative video which walks you through a conventional checkout and one with Amazon Payments enabled (on the All Saints website):
For more imformation, visit the Amazon Payments website